1. Field of the Invention
The present invention relates to a method of generating or modifying a solid model of a structural object, and an apparatus suitable for practicing the method to generate or modify such solid model.
2. Discussion of the Related Art
A solid model generator is used in designing a structural object or solid such as automotive parts, die sets used on a press, or other components of a structural assembly. Such a solid model generator includes a solid modeler adapted to receive data representative of shapes in specified cross sectional planes of the structural object, and data indicative of attributes of such cross sectional shapes. These shapes and attributes cooperate to define the geometry of the object. The solid modeler automatically generates a solid model of the object according to the received cross sectional shapes and the attributes. When a structural assembly such as a part of an automobile or a die set used on a press is modified in design for use on another type of automobile or for partial re-modelling of the automobile, the operator of the solid model generator operates an appropriate data input device to identify the automotive part or die set to be re-designed or modified in design, and select each component of the structural assembly to be displayed on a display screen. The operator further operates the data input device to change the cross sectional shapes and attributes of each component to modify the component, as needed, so that the solid modeler automatically modifies the original solid model, namely, automatically generates a solid model of the component as modified, and display the newly generated solid model of the modified component. The above operation should be repeated for each of the components of the structural assembly that should be modified in design.
The solid model generator indicated above uses a general-purpose CAD (computer-aided design) software for dealing with the operator's commands to designate the desired component to be modified and change object-defining parameters in the form of the cross sectional shapes and attributes described above. The solid modeler operates also according to the CAD software, to generate the solid model of the modified component. Since the solid modeler requires a considerably long processing time to modify the solid model of each component, the operator should wait an accordingly long time, at the site of the peripheral data input device. Where two or more components of the structural assembly in question should be modified in design, the cumulative waiting time of the operator as a designer of the structural assembly is substantially prolonged, leading to unsatisfactory designing efficiency on the side of the designer. In the case of dimensional or geometric modification of the two or more components of the structural assembly, the designer usually considers the compatibility of the modified components with respect to each other and with respect to the non-modified components, in terms of their attachment or connection to or engagement with each other or their dimensional coordination. As a result of these considerations, the designer is sometimes required to re-modify the component or components so as to correct or overcome defects or incompatibility of the modified and non-modified components in a trial-and-error fashion. In such event, two or more processing operations are performed by the solid modeler for each of the components that are modified from their original design, whereby the cumulative or total processing time required by the solid modeler tends to be increased, resulting in reduced designing efficiency.
In some solid model generators, the cross sectional shapes and attributes used to generate solid models of structural components are given by wire frame data representative of two-dimensional wire frame models. Each wire frame model consists of shape definition lines which define a shape or geometry of the appropriate component. Such solid model generators may be adapted such that the initially generated or prepared wire frame models are used to generate the corresponding surface models, so that the corresponding solid models are generated on the basis of the surface models.
In such solid model generators, solid model data representative of solid models of different components (A, B, C) are stored in respective solid model data files, while wire frame data or surface model data are stored in a design-concept data file, together with design concept data which identify the components (A, B, C) constituting an assembly and indicate a positional relationship between the components, as indicated in FIG. 22. Further, relation data indicating a relationship between the solid models of these components and wire frame models or surface frame models represented by the wire frame data or surface model data are stored in a relation data file, as also indicated in FIG. 22. The wire frame data and design concept data stored in the design-concept data file are treated as a unit or a batch of data, and the wire frame data of the component A cannot be retrieved alone, independently of the wire frame data of the component B, for example. When it is desired to use the wire frame model of the component A of the assembly (A, B, C), the wire frame models of all the three components A, B, C are first displayed on a screen such that these three wire frame models are disposed in the positional relationship defined by the design concept data. In this condition, the wire frame data in the design-concept data file are modified so that the wire frame models of the unnecessary components B and C are removed or erased, and the remaining wire frame model of the necessary component A is changed as needed. The thus modified wire frame model data are used to generate a solid model of a new structural assembly which includes the modified component A. If the new structural assembly consists of the component A of the assembly (A, B, C) and another component which is a component of another structural assembly whose wire frame data and design concept data are stored in another design-concept data file, a similar operation should be repeated to generate a solid model of the new assembly. Since the operations required to utilize the already stored wire frame data and design concept data are cumbersome and time-consuming described above, there is a high possibility of operational errors occurring during the modification of the wire frame data (surface model data), and the efficiency of generating a solid model of a structural assembly tends to be low.